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                <ol class="chapter"><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">1.</strong> 类型系统</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../01_类型系统/Rust_Concept_Clarification_Deref_vs_AsRef_vs_Borrow_vs_Cow/Rust_Concept_Clarification_Deref_vs_AsRef_vs_Borrow_vs_Cow.html"><strong aria-hidden="true">1.1.</strong> Rust Concept Clarification Deref vs AsRef vs Borrow vs Cow</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Rust_Concept_Clarification_Deref_vs_AsRef_vs_Borrow_vs_Cow/Deref_AsRef_Borrow_Cow释义.html"><strong aria-hidden="true">1.2.</strong> Deref AsRef Borrow Cow 释义</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Rust的Borrow和AsRef：让你的代码用起来像呼吸一样自然/Rust的Borrow和AsRef：让你的代码用起来像呼吸一样自然.html"><strong aria-hidden="true">1.3.</strong> Rust的Borrow和AsRef：让你的代码用起来像呼吸一样自然</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Rust的Cow类型有什么用？详解Cow及其用途/Rust的Cow类型有什么用？详解Cow及其用途.html"><strong aria-hidden="true">1.4.</strong> Rust的Cow类型有什么用？详解Cow及其用途</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/判别Fn、FnMut、FnOnce的标准/判别Fn、FnMut、FnOnce的标准.html"><strong aria-hidden="true">1.5.</strong> 判别Fn、FnMut、FnOnce的标准</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/一行代码告诉你内部可变性的真相(UnsafeCell)/一行代码告诉你内部可变性的真相(UnsafeCell).html"><strong aria-hidden="true">1.6.</strong> 一行代码告诉你内部可变性的真相(UnsafeCell)</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Tour_of_Rust's_Standard_Library_Traits/Tour_of_Rust's_Standard_Library_Traits.html"><strong aria-hidden="true">1.7.</strong> Tour of Rust's Standard Library Traits</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/逆变、协变与子类型，以及Rust/逆变、协变与子类型，以及Rust.html"><strong aria-hidden="true">1.8.</strong> 逆变、协变与子类型，以及Rust</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Rust自引用结构、Pin与Unpin/Rust自引用结构、Pin与Unpin.html"><strong aria-hidden="true">1.9.</strong> Rust自引用结构、Pin与Unpin</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/为什么Rust需要Pin,Unpin/为什么Rust需要Pin,Unpin.html"><strong aria-hidden="true">1.10.</strong> 译：为什么 Rust 需要 Pin, Unpin ？</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/定海神针Pin和Unpin/定海神针Pin和Unpin.html"><strong aria-hidden="true">1.11.</strong> 译：定海神针 Pin 和 Unpin</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/sizedness-in-rust/sizedness-in-rust.html"><strong aria-hidden="true">1.12.</strong> Sizedness in Rust</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/Rust生命周期集大成者PhantomData〈T〉/Rust生命周期集大成者PhantomData〈T〉.html"><strong aria-hidden="true">1.13.</strong> Rust生命周期集大成者 PhantomData&lt;T&gt;</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：用Rust做类型体操_Part_0.html"><strong aria-hidden="true">1.14.</strong> 数据库表达式执行的黑魔法：用Rust做类型体操 Part 0</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：GAT实现引用类型关联_Part_1.html"><strong aria-hidden="true">1.15.</strong> 数据库表达式执行的黑魔法：GAT实现引用类型关联 Part 1</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：用HRTB写bound_Part_2.html"><strong aria-hidden="true">1.16.</strong> 数据库表达式执行的黑魔法：用HRTB写bound Part 2</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：用Rust做类型体操之用宏展开重复代码_Part_3_&_4.html"><strong aria-hidden="true">1.17.</strong> 数据库表达式执行的黑魔法：用Rust做类型体操之用宏展开重复代码 Part 3 & 4</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：与Rust编译器斗智斗勇之表达式向量化_Part_5_&_6.html"><strong aria-hidden="true">1.18.</strong> 数据库表达式执行的黑魔法：与Rust编译器斗智斗勇之表达式向量化 Part 5 & 6</a></li><li class="chapter-item expanded "><a href="../../01_类型系统/数据库表达式执行的黑魔法：用Rust做类型体操/数据库表达式执行的黑魔法：在Rust中用宏关联逻辑类型和实际类型_Part_7.html"><strong aria-hidden="true">1.19.</strong> 数据库表达式执行的黑魔法：在Rust中用宏关联逻辑类型和实际类型 Part 7</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">2.</strong> 生命周期</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../02_生命周期/Rust中的生命周期——从StrSplit实例说开去/Rust中的生命周期——从StrSplit实例说开去.html"><strong aria-hidden="true">2.1.</strong> Rust中的生命周期——从StrSplit实例说开去</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/与ChatGPT深度对话来学Rust生命周期/与ChatGPT深度对话来学Rust生命周期.html"><strong aria-hidden="true">2.2.</strong> 与ChatGPT深度对话来学Rust生命周期</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/进击的Rust生命周期——early_bound与late_bound（1）/进击的Rust生命周期——early_bound与late_bound（1）.html"><strong aria-hidden="true">2.3.</strong> 进击的Rust生命周期——early_bound与late_bound（1）</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/进击的Rust生命周期——early_bound与late_bound（2）/进击的Rust生命周期——early_bound与late_bound（2）.html"><strong aria-hidden="true">2.4.</strong> 进击的Rust生命周期——early_bound与late_bound（2）</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/进击的Rust生命周期——一力降十会的MIR（1）/进击的Rust生命周期——一力降十会的MIR（1）.html"><strong aria-hidden="true">2.5.</strong> 进击的Rust生命周期——一力降十会的MIR（1）</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/进击的Rust生命周期——一力降十会的MIR（2）/进击的Rust生命周期——一力降十会的MIR（2）.html"><strong aria-hidden="true">2.6.</strong> 进击的Rust生命周期——一力降十会的MIR（2）</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/Common_Rust_Lifetime_Misconceptions/Common_Rust_Lifetime_Misconceptions.html"><strong aria-hidden="true">2.7.</strong> Common Rust Lifetime Misconceptions</a></li><li class="chapter-item expanded "><a href="../../02_生命周期/Rust生命周期常见误区/Rust生命周期常见误区.html"><strong aria-hidden="true">2.8.</strong> 译：Rust生命周期常见误区</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">3.</strong> 无畏并发</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../05_无畏并发/简单写个Rust无锁队列/简单写个Rust无锁队列.html"><strong aria-hidden="true">3.1.</strong> 简单写个Rust无锁队列</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/进击的Rust多线程——混合自旋锁/进击的Rust多线程——混合自旋锁.html"><strong aria-hidden="true">3.2.</strong> 进击的Rust多线程——混合自旋锁</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/An_unsafe_tour_of_Rust's_Send_and_Sync/An_unsafe_tour_of_Rust's_Send_and_Sync.html"><strong aria-hidden="true">3.3.</strong> An unsafe tour of Rust's Send and Sync</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/进击的Rust多线程——Send与Sync/进击的Rust多线程——Send与Sync.html"><strong aria-hidden="true">3.4.</strong> 进击的Rust多线程——Send与Sync</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/进击的Rust多线程——离经叛道的PhantomData/进击的Rust多线程——离经叛道的PhantomData.html"><strong aria-hidden="true">3.5.</strong> 进击的Rust多线程——离经叛道的PhantomData</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/Rust_Async_Pin概念解析/Rust_Async_Pin概念解析.html"><strong aria-hidden="true">3.6.</strong> Rust Async: Pin概念解析</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/Rust和C++的并发库对比/Rust和C++的并发库对比.html"><strong aria-hidden="true">3.7.</strong> 译：Rust 和 C++ 的并发库对比</a></li><li class="chapter-item expanded "><a href="../../05_无畏并发/Rust原子类型和内存排序/Rust原子类型和内存排序.html"><strong aria-hidden="true">3.8.</strong> Rust原子类型和内存排序</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">4.</strong> 网络编程</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../06_网络编程/从编解码层面理解WebSocket_手写一个WebSocket/从编解码层面理解WebSocket_手写一个WebSocket.html"><strong aria-hidden="true">4.1.</strong> 从编解码层面理解WebSocket 手写一 个WebSocket</a></li><li class="chapter-item expanded "><a href="../../06_网络编程/透过Rust探索系统的本原：网络篇/透过Rust探索系统的本原：网络篇.html"><strong aria-hidden="true">4.2.</strong> 透过Rust探索系统的本原：网络篇</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">5.</strong> 轮子系列</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../07_轮子系列/700行Rust写一个内存分配器/700行Rust写一个内存分配器.html"><strong aria-hidden="true">5.1.</strong> 700行Rust写一个内存分配器</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/Rust：网络库的实现思路/Rust：网络库的实现思路.html"><strong aria-hidden="true">5.2.</strong> Rust：网络库的实现思路</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/Rust异步运行时基础部件/Rust异步运行时基础部件.html"><strong aria-hidden="true">5.3.</strong> Rust异步运行时基础部件</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/使用Rust+epoll编写异步IO框架/使用Rust+epoll编写异步IO框架（1）.html"><strong aria-hidden="true">5.4.</strong> 使用Rust+epoll编写异步IO框架（1）</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/使用Rust+epoll编写异步IO框架/使用Rust+epoll编写异步IO框架（2）.html"><strong aria-hidden="true">5.5.</strong> 使用Rust+epoll编写异步IO框架（2）</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/使用Rust+epoll编写异步IO框架/使用Rust+epoll编写异步IO框架（3）.html"><strong aria-hidden="true">5.6.</strong> 使用Rust+epoll编写异步IO框架（3）</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/用rust从零开发一套web框架/用rust从零开发一套web框架：day1.html"><strong aria-hidden="true">5.7.</strong> 用rust从零开发一套web框架：day1</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/用rust从零开发一套web框架/用rust从零开发一套web框架：day2.html"><strong aria-hidden="true">5.8.</strong> 用rust从零开发一套web框架：day2</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/用rust从零开发一套web框架/用rust从零开发一套web框架：day3.html"><strong aria-hidden="true">5.9.</strong> 用rust从零开发一套web框架：day3</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/用rust从零开发一套web框架/用rust从零开发一套web框架：day4.html" class="active"><strong aria-hidden="true">5.10.</strong> 用rust从零开发一套web框架：day4</a></li><li class="chapter-item expanded "><a href="../../07_轮子系列/用rust从零开发一套web框架/用rust从零开发一套web框架：day5.html"><strong aria-hidden="true">5.11.</strong> 用rust从零开发一套web框架：day5</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">6.</strong> 奇技淫巧</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../08_奇技淫巧/Copy-On-Write是不是优化？/Copy-On-Write是不是优化？.html"><strong aria-hidden="true">6.1.</strong> 译：Copy-On-Write是不是优化？</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/揭秘神奇的Rust_Axum风格的函数实现/揭秘神奇的Rust_Axum风格的函数实现.html"><strong aria-hidden="true">6.2.</strong> 译：揭秘神奇的 Rust Axum 风格的函数实现</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/“变长参数”函数与回调/“变长参数”函数与回调.html"><strong aria-hidden="true">6.3.</strong> “变长参数”函数与回调</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/Rust字符串格式化的幕后：format_args!()/Rust字符串格式化的幕后：format_args!().html"><strong aria-hidden="true">6.4.</strong> 译：Rust字符串格式化的幕后：format_args!()</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/给Rust带来一点C++特产/给Rust带来一点C++特产.html"><strong aria-hidden="true">6.5.</strong> 给Rust带来一点C++特产</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/一步步实现_Rust_Bevy_ECS_的_System_简化版本/一步步实现_Rust_Bevy_ECS_的_System_简化版本.html"><strong aria-hidden="true">6.6.</strong> 一步步实现 Rust Bevy ECS 的 System 简化版本</a></li><li class="chapter-item expanded "><a href="../../08_奇技淫巧/Exploring_Design_Patterns_in_Rust_with_Algorithmic_Trading_Examples/Exploring_Design_Patterns_in_Rust_with_Algorithmic_Trading_Examples.html"><strong aria-hidden="true">6.7.</strong> Exploring Design Patterns in Rust with Algorithmic Trading Examples</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">7.</strong> 源码分析</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../09_源码分析/Rust并发：bytes源码分析/Rust并发：bytes源码分析.html"><strong aria-hidden="true">7.1.</strong> Rust并发：bytes源码分析</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust并发：标准库Arc源码分析/Rust并发：标准库Arc源码分析.html"><strong aria-hidden="true">7.2.</strong> Rust并发：标准库Arc源码分析</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust并发：标准库sync_Once源码分析/Rust并发：标准库sync_Once源码分析.html"><strong aria-hidden="true">7.3.</strong> Rust并发：标准库sync::Once源码分析</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust源码阅读：引用计数Rc/Rust源码阅读：引用计数Rc.html"><strong aria-hidden="true">7.4.</strong> Rust源码阅读：引用计数Rc</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust源码阅读：Cell、RefCell与内部可变性/Rust源码阅读：Cell、RefCell与内部可变性.html"><strong aria-hidden="true">7.5.</strong> Rust源码阅读： Cell、RefCell与内部可变性</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/关于_Rust_的_UnsafeCell、Cell_与_RefCell/关于_Rust_的_UnsafeCell、Cell_与_RefCell.html"><strong aria-hidden="true">7.6.</strong> 关于 Rust 的 UnsafeCell、Cell 与 RefCell</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust_Async_async-stream源码分析/Rust_Async_async-stream源码分析.html"><strong aria-hidden="true">7.7.</strong> Rust Async: async-stream源码分析</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/走进Tokio的异步世界/走进Tokio的异步世界.html"><strong aria-hidden="true">7.8.</strong> 走进 Tokio 的异步世界</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/tokio.rs_runtime的实现/tokio.rs_runtime的实现.html"><strong aria-hidden="true">7.9.</strong> tokio.rs runtime 的实现</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Tokio_internals/Tokio_internals.html"><strong aria-hidden="true">7.10.</strong> Tokio internals</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Tokio_internals/译文：Tokio內部机制.html"><strong aria-hidden="true">7.11.</strong> 译：Tokio 内部机制</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Rust_Axum_HTTP_框架的架构分析/Rust_Axum_HTTP_框架的架构分析.html"><strong aria-hidden="true">7.12.</strong> Rust Axum HTTP 框架的架构分析</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/安利一个Rust_Game_Engine：Bevy--ECS部分/安利一个Rust_Game_Engine：Bevy--ECS部分.html"><strong aria-hidden="true">7.13.</strong> 安利一个Rust Game Engine：Bevy--ECS部分</a></li><li class="chapter-item expanded "><a href="../../09_源码分析/Tokio_解析之任务调度/Tokio_解析之任务调度.html"><strong aria-hidden="true">7.14.</strong> Tokio 解析之任务调度</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">8.</strong> 生态观察</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../11_生态观察/Rust_web_frameworks_have_subpar_error_reporting/Rust_web_frameworks_have_subpar_error_reporting.html"><strong aria-hidden="true">8.1.</strong> Rust web frameworks have subpar error reporting</a></li><li class="chapter-item expanded "><a href="../../11_生态观察/SeaORM：要做Rust版本的ActiveRecord/SeaORM：要做Rust版本的ActiveRecord.html"><strong aria-hidden="true">8.2.</strong> SeaORM：要做Rust版本的ActiveRecord</a></li></ol></li><li class="chapter-item expanded "><a href="../../empty.html"><strong aria-hidden="true">9.</strong> 死灵终极</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_总述.html"><strong aria-hidden="true">9.1.</strong> 译：Learn Rust the Dangerous Way 总述</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_0.html"><strong aria-hidden="true">9.2.</strong> 译：Learn Rust the Dangerous Way 0</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_1.html"><strong aria-hidden="true">9.3.</strong> 译：Learn Rust the Dangerous Way 1</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_2.html"><strong aria-hidden="true">9.4.</strong> 译：Learn Rust the Dangerous Way 2</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_3.html"><strong aria-hidden="true">9.5.</strong> 译：Learn Rust the Dangerous Way 3</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_4.html"><strong aria-hidden="true">9.6.</strong> 译：Learn Rust the Dangerous Way 4</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Learn_Rust_the_Dangerous_Way_系列文章翻译/Learn_Rust_the_Dangerous_Way_系列文章翻译_5.html"><strong aria-hidden="true">9.7.</strong> 译：Learn Rust the Dangerous Way 5</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Unsafe_Rust_随堂小测/Unsafe_Rust_随堂小测（一）.html"><strong aria-hidden="true">9.8.</strong> Unsafe Rust 随堂小测（一）</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Unsafe_Rust_随堂小测/Unsafe_Rust_随堂小测（二）.html"><strong aria-hidden="true">9.9.</strong> Unsafe Rust 随堂小测（二）</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Unsafe_Rust_随堂小测/Unsafe_Rust_随堂小测（三）.html"><strong aria-hidden="true">9.10.</strong> Unsafe Rust 随堂小测（三）</a></li><li class="chapter-item expanded "><a href="../../12_死灵终极/Unsafe_Rust_随堂小测/Unsafe_Rust_随堂小测参考答案.html"><strong aria-hidden="true">9.11.</strong> Unsafe Rust 随堂小测参考答案</a></li></ol></li></ol>
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                        <h1 id="用-rust-从零开发一套-web-框架day4"><a class="header" href="#用-rust-从零开发一套-web-框架day4">用 rust 从零开发一套 web 框架：day4</a></h1>
<p><a href="https://juejin.cn/user/677714513628055/posts">linken_coding</a></p>
<p>2022-12-062,489阅读6分钟</p>
<p>专栏： </p>
<p>rust从零开发轮子系列</p>
<p>开启掘金成长之旅！这是我参与「掘金日新计划 · 12 月更文挑战」的第8天，<a href="https://juejin.cn/post/7167294154827890702">点击查看活动详情</a></p>
<h2 id="元婴出窍"><a class="header" href="#元婴出窍">元婴出窍</a></h2>
<p>前面我们实现了动态路由解析，总算是把最难的一关给跨过去了。那今天在上一章的基础上，实现一些简单点的路由分组功能。</p>
<h2 id="分组的意义"><a class="header" href="#分组的意义">分组的意义</a></h2>
<p>分组控制(Group Control)是 Web 框架应提供的基础功能之一。所谓分组，是指路由的分组。如果没有路由分组，我们需要针对每一个路由进行控制。但是真实的业务场景中，往往某一组路由需要相似的处理。例如：</p>
<p>以<code>/user</code>开头的路由匿名可访问。 以<code>/admin</code> 开头的路由需要鉴权。 以<code>/api</code> 开头的路由是 <code>RESTful</code> 接口，可以对接第三方平台，需要三方平台鉴权。 大部分情况下的路由分组，是以相同的前缀来区分的。因此，我们今天实现的分组控制也是以前缀来区分，并且支持分组的嵌套。例如<code>/user</code> 是一个分组，<code>/user/a</code> 和<code>/user/b</code> 可以是该分组下的子分组。作用在<code>/user</code> 分组上的中间件(middleware)，也都会作用在子分组，子分组还可以应用自己特有的中间件。</p>
<p>中间件可以给框架提供无限的扩展能力，应用在分组上，可以使得分组控制的收益更为明显，而不是共享相同的路由前缀这么简单。例如<code>/admin</code> 的分组，可以应用鉴权中间件；/分组应用日志中间件，/是默认的最顶层的分组，也就意味着给所有的路由，即整个框架增加了记录日志的能力。</p>
<p>提供扩展能力支持中间件的内容，我们将在下一节当中介绍。</p>
<h2 id="分组嵌套"><a class="header" href="#分组嵌套">分组嵌套</a></h2>
<p>一个 Group 对象需要具备哪些属性呢？首先是前缀(prefix)，比如<code>/</code>，或者<code>/admin</code>；要支持分组嵌套，那么需要知道当前分组的父亲(parent)是谁；当然了，按照我们一开始的分析，中间件是应用在分组上的，那还需要存储应用在该分组上的中间件(middlewares)。还记得，我们之前调用函数 <code>add_route()</code>来映射所有的路由规则和 <code>Handler</code> 。如果 <code>Group</code> 对象需要直接映射路由规则的话，比如我们想在使用框架时，这么调用：</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let mut router = Router::new();

let g1 = router.group(&quot;/admin&quot;);
    g1.get(&quot;/hello&quot;, |c: &amp;mut AppContext| {
        let s = format!(&quot;hello world from admin&quot;);
        c.string(None, &amp;s)
    })
    .get(&quot;/index&quot;, |c: &amp;mut AppContext| {
        let s = format!(&quot;hello world from index&quot;);
        c.string(None, &amp;s)
    });
<span class="boring">}
</span></code></pre></pre>
<p>因为<code>/admin</code>路由分组本质上其实也是路由，但是直接把整个路由 Router 结构体嵌套进去的话，似乎也不太合适。因为这样会获取数据的所有权。</p>
<p>所以我定义的路由分组是这样的：</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>///路由组，对路由进行分组控制
pub struct RouterGroup&lt;'a&gt; {
    path: String,
    router: &amp;'a mut Router,
}
<span class="boring">}
</span></code></pre></pre>
<p><code>RouterGroup</code>只得到路由<code>Router</code>的可变引用，这样就不必复制<code>Router</code>的内容到<code>RouterGroup</code>里面造成数据重复的多余性能开销和所有权冲突。 那么，接下来，为<code>RouterGroup</code>实现一系列的路由操作：</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>impl&lt;'a&gt; RouterGroup&lt;'a&gt; {
    fn new(path: &amp;str, router: &amp;'a mut Router) -&gt; Self {
        Self {
            path: path.to_string(),
            router,
        }
    }
    fn add&lt;F&gt;(self, path: &amp;str, method: Method, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        let mut join_path = String::new();
        if self.path.as_str() == &quot;/&quot; {
            join_path.push_str(path);
        } else if path == &quot;/&quot; {
            join_path.push_str(self.path.as_str());
        } else {
            join_path = format!(&quot;{}{}&quot;, self.path, path)
        }
        self.router.add(&amp;join_path, method, handler);
        self
    }

    /// 封装各类请求
    pub fn get&lt;F&gt;(self, path: &amp;str, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, Method::GET, handler)
    }

    pub fn post&lt;F&gt;(self, path: &amp;str, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, Method::POST, handler)
    }

    pub fn put&lt;F&gt;(self, path: &amp;str, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, Method::PUT, handler)
    }

    pub fn patch&lt;F&gt;(self, path: &amp;str, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, Method::PATCH, handler)
    }

    pub fn delete&lt;F&gt;(self, path: &amp;str, handler: F) -&gt; Self
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, Method::DELETE, handler)
    }
}
<span class="boring">}
</span></code></pre></pre>
<p>封装好路由的增删改查操作和<code>RouterGroup</code>的初始化。注意：这里的方法，都是传入<code>self</code>作为参数，和之前的<code>Router</code>实现的增删改查一样，有兴趣的同学可以思考一下能否改为 <code>&amp;mut self</code> 或者<code>mut self</code>。改动之后，又会有什么样的变化。</p>
<p>另外，细心的同学可能发现了，<code>router</code> 中需要新增一个分组<code>group</code>方法。</p>
<p>同时新增路由的方法似乎变为了<code>add</code>,我们来看一下<code>Router</code>实现的<code>add</code>函数和之前的<code>add_router</code>有何区别:</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>impl Router {
    ...
    /// 路由分组
    pub fn group(&amp;mut self, path: &amp;str) -&gt; RouterGroup {
        RouterGroup::new(path, self)
    }

   //分组新增路由
    fn add&lt;F&gt;(&amp;mut self, path: &amp;str, method: Method, handler: F)
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        let key = format!(&quot;{}+{}&quot;, method.as_ref(), path);
        self.handlers.insert(key, Box::new(handler));
        let parts = parse_pattern(path);
        self.roots.insert(method.clone(), path, parts.clone(), 0);
    }

    //新增路由
    fn add_route&lt;F&gt;(mut self, path: &amp;str, method: Method, handler: F) -&gt; Router
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        let key = format!(&quot;{}+{}&quot;, method.as_ref(), path);
        self.handlers.insert(key, Box::new(handler));
        let parts = parse_pattern(path);
        self.roots.insert(method.clone(), path, parts.clone(), 0);
        self
    }
}
<span class="boring">}
</span></code></pre></pre>
<p>不看不知道，一看吓一跳。这不是一模一样的函数吗？没错，这两个函数几乎就就一样的。但是吧，只有一个地方不一样，就是一个入参是<code>mut self</code>，另一个是<code>&amp;mut self</code>。可别小看这个<code>&amp;</code>，这里面区别可大了。一个拥有 <code>self</code> 的所有权，一个是借用。如果你想偷懒，把二者合并为一。那你就准备接受编译器的毒打吧 😄。 当然了，同样可以想办法压缩一下冗余代码：</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>impl Router {
    ...
    //新增路由
    fn add_route&lt;F&gt;(mut self, path: &amp;str, method: Method, handler: F) -&gt; Router
    where
        F: Fn(&amp;mut AppContext) + Send + Sync + 'static,
    {
        self.add(path, method, handler);
        self
    }
}
<span class="boring">}
</span></code></pre></pre>
<p>接下来，进行测试一下效果，在 main 函数写上分组的<code>group</code>：</p>
<pre><pre class="playground"><code class="language-rust">#[tokio::main]
async fn main() {
    let handle_hello = |c: &amp;mut AppContext| c.string(None, &quot;hello world from handler&quot;);

    let mut router = Router::new().get(&quot;/user&quot;, handle_hello).get(&quot;/ghost/:id&quot;, handle_hello);

    let g1 = router.group(&quot;/admin&quot;);

    g1.get(&quot;/hello&quot;, |c: &amp;mut AppContext| {
        let s = format!(&quot;hello world from admin&quot;);
        c.string(None, &amp;s)
    })
    .get(&quot;/index&quot;, |c: &amp;mut AppContext| {
        let s = format!(&quot;hello world from index&quot;);
        c.string(None, &amp;s)
    });

    // Run the server like above...
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));

    server::run(addr, router).await;
}
</code></pre></pre>
<p>然后在浏览器中分别打开：<code>http://localhost:3000/admin/index</code>和<code>http://localhost:3000/admin/hello</code></p>
<p>同时，查看终端生成的路由节点树：</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>当前节点：RouterNode {
    pattern: None,
    part: None,
    children: [
        RouterNode {
            pattern: Some(
                &quot;/user&quot;,
            ),
            part: None,
            children: [],
            is_match: false,
            hooks: [],
            method: Some(
                &quot;GET&quot;,
            ),
        },
        RouterNode {
            pattern: Some(
                &quot;/ghost&quot;,
            ),
            part: None,
            children: [
                RouterNode {
                    pattern: Some(
                        &quot;/ghost/:id&quot;,
                    ),
                    part: Some(
                        &quot;:id&quot;,
                    ),
                    children: [],
                    is_match: true,
                    hooks: [],
                    method: Some(
                        &quot;GET&quot;,
                    ),
                },
            ],
            is_match: false,
            hooks: [],
            method: None,
        },
        RouterNode {
            pattern: Some(
                &quot;/admin&quot;,
            ),
            part: None,
            children: [
                RouterNode {
                    pattern: Some(
                        &quot;/admin/hello&quot;,
                    ),
                    part: None,
                    children: [],
                    is_match: false,
                    hooks: [],
                    method: Some(
                        &quot;GET&quot;,
                    ),
                },
                RouterNode {
                    pattern: Some(
                        &quot;/admin/index&quot;,
                    ),
                    part: None,
                    children: [],
                    is_match: false,
                    hooks: [],
                    method: Some(
                        &quot;GET&quot;,
                    ),
                },
            ],
            is_match: false,
            hooks: [],
            method: None,
        },
    ],
    is_match: false,
    hooks: [],
    method: None,
}
<span class="boring">}
</span></code></pre></pre>
<p>现在加上路由分组，我们在路由控制上面更近一步。当然，这一章可以说是相当简单的，毕竟难度都在前面的路由节点树上面了，路由分组功能只不过是锦上添花而已。</p>

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